Materials Included In Kit

Additional Materials Required

Prelab Preparation

To prepare unknown samples of the OTC drugs: Use a mortar and pestle to grind up an OTC drug tablet until it is fully powdered. Place one or two small scoopfuls of the powder in a vial or test tube. Label the test tube or vial with an unknown number. Distribute an unknown sample to each group of students.

Safety Precautions

Do not allow students to ingest any of the over-the-counter drug samples during this laboratory. The samples are for laboratory use only, have been stored with other non–food-grade laboratory chemicals and are not meant for human consumption. Hydrochloric acid solution is toxic by ingestion and inhalation and is corrosive to skin and eyes. Iron(III) nitrate solution may be a skin/tissue irritant. Universal indicator solution is a flammable, alcohol-based solution. Avoid contact of all chemicals with eyes and all body tissues. Wear chemical splash goggles, chemical-resistant gloves and a chemical-resistant apron. Please review current Safety Data Sheets for additional safety, handling and disposal information.

Disposal

Please consult your current Flinn Scientific Catalog/Reference Manual for general guidelines and specific procedures, and review all federal, state and local regulations that may apply, before proceeding. The contents of the wells of the reaction plates may be rinsed down the drain with plenty of water according to Flinn Suggested Disposal Method #26b. Remaining OTC drug samples can be disposed of in the solid waste disposal according to Flinn Suggested Disposal Method #26a.

Teacher Tips

• Enough materials are provided for 30 students working in pairs or for 15 groups of students.
• This kit contains 20 tablets of each OTC drug (except Alka-Seltzer^®). This is enough to give each of the 15 groups one tablet of each, leaving 5 extra tablets of each for the unknown samples. Due to the large size of each Alka-Seltzer tablet, one tablet can be crushed up and shared by at least two groups. For this reason, 10 tablets is more than enough.
• Take precautions with the OTC drug samples. The following suggestions are recommended: Do not leave the bottles containing the OTC drug samples out on the laboratory table. Do not allow students to help themselves to the drug samples. Hand out ONE tablet of each OTC drug to each student group. Keep the bottles locked up. Remember, these are actual drugs and can cause harm or even fatality if misused.
• Unknowns—Extras of each of the OTC drug samples are provided in the kit to be used for the unknown samples. These tablets will need to be ground up prior to lab. Due to the additives/inactive ingredients in the tablets (e.g., sugars, starches, other fillers), we found that the pure chemicals gave significantly different reactions. For example, pure powdered acetylsalicylic acid was tested so that this might be provided as the unknown for the aspirin. Results when comparing the aspirin tablet to the pure acetylsalicylic acid were very different. It seems that the inactive ingredients in the OTC tablets cause changes in the results in terms of pH, color with universal indicator and reaction with iron(III) nitrate. The same was true when calcium carbonate was tested as the possible unknown for the generic antacid. Therefore, unknown powdered samples are not provided with this kit—instead extra OTC drug tablets are included. For information, see the Prelab Preparation section.
• If a mortar and pestle are not available, have students place the tablets on a piece of paper. Fold the paper over the tablet and gently tap to crush the tablet using a solid, unbreakable object (e.g., pen).

Further Extensions

This lab can be easily extended to a cross-curricular creative writing activity. Combine scientific qualitative analysis with writing by having students develop a “crime scene” scenario dealing with OTC drugs.

Sample Data

Answers to Questions

Part I Questions

1. The unknown pain reliever for Part Ib was unknown # _______.
2. Which unknown pain reliever did you have? Analyze your data from Part I and list all evidence for choosing this pain reliever.

   Student answers will vary.

3. Which of the five pain relievers tested was the most acidic? Which was the least acidic?

   The most acidic pain relievers are aspirin with a pH of 2 and Excedrin with a pH of 2–3. The least acidic pain reliever is Bufferin with a pH of 5.

4. Did the pH (acidity) of any of the pain relievers change over time? Which? Explain.

   The pH of Bufferin changes over time. It starts out with a pH of approximately 5 and over time becomes more neutral, reaching a pH of approximately 7. This is due to the “buffering” effect of the added weak bases to the acidic aspirin. The relatively insoluble bases are slowly released from the tablet to maintain a high enough pH to avoid stomach irritation.

5. When the “simulated stomach acid” (0.5 M HCl) was added to the pain relievers, what happened to the pH? Did any pain relievers resist a drastic drop in pH? Explain.

   When the acid was added to the pain relievers, the pH dropped to a pH of 1 in all cases except for the Bufferin. This one dropped immediately to a pH of 2, and then over time rose back up to approximately 4 or 5, showing its “buffering action.” The actual stomach doesn’t go to 4 or 5, however, because the amount of Bufferin added compared to the volume of the whole stomach is small. Here it is nearly equal.

6. Compare the structures of acetylsalicylic acid, acetaminophen, and ibuprofen from the background section. What similarities do you notice in terms of structure? What differences?

   The structures of the three pain relievers are similar in that they all contain the benzene ring structure and have two side chains off the ring. The differences include the nature of the side chains. Acetylsalicylic acid contains an acetyl ester group and carboxylic acid group in the ortho position (positions 1 and 2). Acetaminophen contains a hydroxy group and an acetyl amide group in the para position (positions 1 and 4)—this compound is in the class known as the p-amidophenols. Ibuprofen contains a carboxylic acid group and an iso-butyl group in the para position.

7. The unknown antacid for Part IIb was unknown #_______.
8. Which unknown antacid did you have? Analyze your data from Part II and list all evidence for choosing this antacid.

   Student answers will vary.

9. Why are most antacids fairly insoluble in water? Hint: Refer to the background section.

   Most antacids are fairly insoluble in water. The low solubility allows the antacid tablet to dissolve slowly in the acidic stomach, releasing carbon dioxide gas gradually as the antacid neutralizes HCl.

10. Compare the pH of the three antacids tested before adding HCl. Then compare the pH of the three antacids after adding HCl, “stomach acid”. Which antacid(s) seem to be most effective? Which antacid(s) seem to be least effective? Explain.

    The pH of Alka-Seltzer is 7–8 before adding the acid and drops to 5 after adding the acid. The pH of Acid Controller Complete is 8–9 before adding acid and drops to a pH of 6 after adding acid. The pH of the generic antacid is 6 before adding acid and drops to a pH of 1 after adding acid. Both the Alka-Seltzer and the Acid Controller Complete are effective at neutralizing the stomach acid, while the generic antacid is ineffective.

References

Eby, D. and Tatum, R. The Chemistry of Over-the-Counter Drugs; Flinn Scientific: Batavia, IL, 1989.

Pavia, D. L.; Lampman, G. M.; Kriz, G. S. Introduction to Organic Laboratory Techniques, 2nd edition; Saunders College Publishing: Philadelphia, 1982; pp 29–37.

Snyder, C. H. The Extraordinary Chemistry of Ordinary Things; John Wiley & Sons: New York, 1992; pp 281–284 and 603–609.

Introduction

Learn to analyze and identify over-the-counter (OTC) drugs including common pain relievers, such as aspirin and acetaminophen, and antacids, such as Alka-Seltzer^®. Test physical and chemical properties of actual OTC drug samples and then use test results to analyze unknown pain reliever and antacid samples.

Concepts

• Qualitative analysis detection techniques
• Chemical reactions of OTC drugs
• Physical properties of OTC drugs

Background

A drug is a chemical used medicinally for treating diseases and injuries. The term “drug,” however, often carries with it the connotation of narcotics, addiction and crime. Many drugs or medicines are entirely legal, readily available, and are sold as over-the-counter medications without the need for a prescription. Over-the-counter (OTC) drugs include categories of drugs such as pain relievers, antacids, alcohol, caffeine and vitamins. While these OTC drugs are sold legally they, like controlled or prescription drugs, have the ability to cause accidental or purposeful poisoning and even death if taken improperly. Thus it is important that dosage information and precautions printed on the label are strictly followed in order to prevent accidental injury or harm.

The first class of OTC drugs tested will be pain relievers—specifically aspirin, acetaminophen, ibuprofen, Bufferin^® and Excedrin^®. Aspirin, the common or trade name for acetylsalicylic acid, is today’s leading commercial pain reliever. Aspirin acts as an analgesic (pain reliever), an antipyretic (fever reducer) and an anti-inflammatory agent (inflammation reducer). Aspirin is a fairly acidic compound which reacts slowly with moisture from the air to undergo hydrolysis, forming salicylic acid and acetic acid (vinegar), as shown in Equation 1.

Thus if aspirin is to be stored for several months, it should be kept dry. If the tablets pick up moisture, they may begin to smell like vinegar and become even more acidic. This increased acidity can be very irritating to the lining of the stomach and intestines, causing side effects such as upset stomach, gastrointestinal bleeding, and various allergic reactions. Furthermore, aspirin, as with any drug, must get into the bloodstream in order to do its work. The time it takes for the acetylsalicylic acid in tablet form to enter the blood is limited by the rate at which the tablet disintegrates in the stomach, which is dependent on pH. The higher the pH (less acidic), the faster the tablet disintegrates.

For these reasons, some people opt to take a buffered aspirin, which contains aspirin and one or more weak bases. Bufferin^® is a brand of buffered aspirin containing aspirin, calcium carbonate, magnesium oxide, and magnesium carbonate. The combination of aspirin and weak bases increases the pH, thus helping with the disintegration of the tablet and hence the absorption of the acetylsalicylic acid into the blood stream. The weak bases in buffered aspirin reduce the acidity that results from the hydrolysis of aspirin in the acidic juices of the stomach; thus, buffered aspirin is found to be less irritating to the stomach lining than aspirin.

The acetylsalicylic acid (aspirin) molecule has an ester side chain group, as shown in Figure 1. The ester group hydrolyzes in the presence of water, leaving an alcohol group (–OH) on the benzene ring, or a phenol compound. A chemical test to detect the presence of the phenol group is seen in the reaction with iron(III) nitrate. When a phenol group is present, a distinct violet-colored complex is formed. Therefore iron(III) nitrate is commonly used as a positive indicator test of the phenol group (and thus for aspirin which easily undergoes hydrolysis).

Acetaminophen, a non-aspirin headache remedy, is another important OTC pain reliever. Acetaminophen, which is an acylated aromatic amine as shown in Figure 2, is the active ingredient in Tylenol^®. Compare Figures 1 and 2 and notice the similarities and differences between the chemical structures of the two pain relievers. Notice that acetaminophen has an alcohol group (–OH) on the benzene ring, also known as a phenol group. Thus, in the presence of iron(III) nitrate, a distinct violet-colored complex is produced due to the reaction of iron(III) nitrate with the phenol group. Acetaminophen acts as a mild analgesic and antipyretic, but lacks anti-inflammatory properties. Acetaminophen is a less acidic alternative to aspirin for those who have an allergic reaction or who find that aspirin produces stomach disorders. Excedrin^® is a combination OTC pain reliever, consisting of equal amounts of aspirin and acetaminophen, and a small amount of caffeine. The caffeine is added as a stimulant to the nervous system and heart, providing a heightened sense of awareness that some people want in a pain reliever.

Ibuprofen, another commonly used pain reliever, is the active ingredient in Advil^®. Ibuprofen, shown in Figure 3, is another non-aspirin OTC drug. However, like aspirin, ibuprofen acts as an analgesic (pain reliever), an antipyretic (fever reducer) and an anti-inflammatory agent (inflammation reducer). Compare Figures 1, 2 and 3, noticing the similarities and differences among the chemical structures of the three molecules.

The second class of OTC drugs tested will be antacids—specifically Alka-Seltzer^®, Acid Controller Complete^® and a genericant acid containing calcium carbonate. Antacids are chemicals that relieve over-acidity by neutralizing excess acid in the stomach. This excess acid can produce discomforts, commonly called “acid indigestion” or “heartburn,” and possibly gastric ulcers. Antacids promise to provide “prompt relief” of the unpleasant effects of these stomach distresses. Most antacids will not dissolve completely in water and are made to dissolve slowly in the acidic juices of the stomach so carbon dioxide will be given off gradually as the antacid neutralizes excess acid.

The stomach’s digestive juices, or gastric juices, contain hydrochloric acid (HCl), which serves to promote digestion of food proteins by the enzyme pepsin in the gastric juices and kill bacteria that enters our digestive system. The stomach lining of a normal adult produces two to three liters of dilute HCl each day to aid in digestion, with a normal stomach pH ranging from 1.0 to 3.0. While the stomach produces a small amount of acid all the time, it can be stimulated to produce more acid in the presence of food. Too much food, certain types of food, or high levels of stress may cause the stomach to respond with an outpouring of acid, thus lowering the stomach pH to the point of discomfort.

Most common antacids contain weak bases such as sodium bicarbonate, calcium carbonate, magnesium hydroxide, aluminum hydroxide, or various combinations of these. The basic compounds in the antacids serve to neutralize excess HCl as well asto affect the functioning of the enzyme pepsin. An acid–base neutralization reaction occurs between the base and the acid in the stomach. An effective antacid does not bring the pH of the stomach fluid to complete acid–base neutrality (pH of 7) as this would completely shut down digestion and promote “acid rebound”—an automatic response which floods the stomach with fresh acid. Instead, an effective antacid neutralizes some of the HCl in the gastric juices—enough to relieve the pain and discomfort, yet still allowing for the continuation of normal digestive processes.

Carbonate-containing antacids, such as sodium bicarbonate, react with stomach acid to produce a neutral salt and carbonic acid. Carbonic acid is a much weaker acid than HCl and decomposes readily to yield carbon dioxide and water, as shown in Equation 2. Hydroxide-containing compounds, such as magnesium hydroxide, react with the acid to produce its neutral salt and water, as shown in Equation 3.

Alka-Seltzer is a popular antacid and pain relief medicine, containing aspirin, citric acid, and sodium bicarbonate (baking soda). When the tablet is dropped into water, the bicarbonate and the citric acid dissolve, producing the familiar “fizz” from the chemical release of carbon dioxide. Complete Acid Controllers are another common type of antacid, containing a combination of calcium carbonate and magnesium hydroxide. The first types of antacids, such as traditional Tums^®, are formulated with only calcium carbonate. Individuals with high blood pressure are advised to avoid excess sodium and may choose to use an antacid without sodium bicarbonate. People with osteoporosis or those who need a calcium supplement may choose an antacid formulated with calcium carbonate. Calcium carbonate, however, if used over long periods of time tends to cause constipation. Thus some antacids contain a combination of calcium carbonate and magnesium hydroxide. This combination tends to overcome the constipation as magnesium hydroxide produces an opposite laxative effect. Magnesium hydroxide, while effective in controlling ulcer pain, has a lower neutralizing capacity and can cause trouble if taken too frequently by people with kidney impairment. In any case, each OTC drug must be taken with caution, and dosage information printed on the label should be strictly followed.

In this laboratory activity, two classes of over-the-counter drugs will be analyzed—pain relievers and antacids. Known samples will be tested, and then unknown samples will be identified by comparison with the known samples. This process of determining the identities of unknown substances by comparison to known substances is called qualitative analysis. This can be contrasted to quantitative analysis, the process of determining how much of a given component is present in a sample. Qualitative analysis procedures involve using physical and/or chemical tests, both of which will be performed here.

Materials

Prelab Questions

1. Read the Background information provided in this handout.
2. On Data Tables 1 and 2, fill in the list of active ingredients that are found in each of the known over-the-counter drugs that you will be testing. This information can be found in the Background section of this handout or on the bottle containing the OTC drug.

Safety Precautions

Do not ingest any of the over-the-counter drug samples during this laboratory. The samples are for laboratory use only, have been stored with other non–food-grade laboratory chemicals, and are not meant for human consumption. Hydrochloric acid solution is toxic by ingestion and inhalation and is corrosive to skin and eyes. Iron(III) nitrate solution may be a skin/tissue irritant. Universal indicator solution is a flammable, alcohol-based solution. Avoid contact of all chemicals with eyes and all body tissues. Wear chemical splash goggles, chemical-resistant gloves and a chemical-resistant apron. Wash hands thoroughly with soap and water before leaving the laboratory.

Procedure

Part Ia. Known OTC Drug Testing—Pain Relievers

1. Place a 24-well reaction plate on a sheet of white paper on the lab bench. Label the sheet of paper as indicated in Data Table 1.
2. Use a mortar and pestle to grind up a single tablet of the first pain reliever, aspirin.
3. Use a spatula to add a few granules of powdered aspirin to each of the four wells of column 1 of the well plate. Save the remaining powdered aspirin in a labeled test tube—in case a test needs to be repeated later.
4. Clean the mortar and pestle by wiping both with a dry paper towel.
5. Repeat steps 2–4 for the remaining four OTC pain reliever tablets. Place a few granules of powdered acetaminophen in each well of column 2 of the well plate, ibuprofen in column 3, Bufferin in column 4 and Excedrin in column 5. Leave column 6 empty—this will be used for the unknown pain reliever sample.

• Row A—Appearance/Solubility
  6. Make detailed observations about the appearance of each powder, noting the color and consistency of each. Record observations of appearance in row A of Data Table 1.
  7. Using a dropper pipet, add 10–15 drops of distilled or deionized water to each of the five powders across row A.
  8. Observe any physical or chemical changes that occur (e.g., fizzing or dissolving). Record observations in row A of Data Table 1.
  9. Stir each well of row A with a toothpick. Observe and record the solubility of each powdered OTC pain reliever in Data Table 1. Use the following guidelines to determine the solubility of each
     • If the resulting solution is clear, then the drug is soluble.
     • If the resulting solution is cloudy, then the drug is slightly soluble.
     • If the powder remains unchanged and there is a thick white precipitate, then the drug is insoluble.
  Note: To avoid contamination while stirring, use five toothpicks (e.g., one toothpick for aspirin, one for acetaminophen).
• Row B—Acidity/pH
  10. Using a dropper pipet, add 10 drops of distilled or deionized water to each of the five powders across row B. Stir.
  11. Using a different dropper pipet, add 3–4 drops of universal indicator solution to each well of row B. Record the color of each solution in row B of Data Table 1. Be very specific when describing the color so as to distinguish between the wells. Note the approximate pH of each solution by comparing the color to the universal indicator color chart.
  12. Determine an accurate pH of each OTC drug by dipping one end of a strip of 1–12 pH paper into each of the corresponding wells of row B. Save resources by using each end of the pH paper for a different well. Use the color chart on the pH paper tube to determine the pH. Record the pH of each in row B of Data Table 1. Note: Monitor the color in the wells of row B as the lab progresses. Watch for any changes in color over time. For any wells that do change color, be sure to retest the pH using a fresh pH strip and record data in Data Table 1.
• Row C—Reaction With HCl, “Simulated Stomach Acid”
  13. Using a dropper pipet, add 10 drops of 0.5 M HCl “simulated stomach acid” solution to each well of row C.
  14. Stir each well of Row r with a toothpick. Observe any reactions that occur as noted by fizzing (slight or vigorous) or dissolving (insoluble, slightly soluble or fully soluble). Record detailed observations in row C of Data Table 1.
  15. Determine the pH of each OTC pain reliever in the “stomach” by dipping one end of a strip of 1–12 pH paper into each of the corresponding wells of row C. Save resources by using each end of the pH paper for a different well. Use the color chart on the pH paper tube to determine the pH. Record the “stomach” pH of each in row C of Data Table 1.
• Row D—Reaction With Iron(III) Nitrate
  16. Using a dropper pipet, add 10 drops of 0.2 M Fe(NO₃)₃ solution to each well of row D.
  17. Stir each well of row D with a toothpick. Observe any reactions that occur as noted by fizzing or color changes. Record detailed observations of each solution in row D of Data Table 1. Be very specific when describing the color so as to distinguish between the wells.
  18. Repeat any tests that gave unclear results using the remaining pain relievers that were saved earlier. Go on to Part Ib—testing an unknown OTC pain reliever. Do not rinse out the well plate until Part Ib is completed.

Part Ib. Unknown OTC Drug Testing—Pain Relievers

19. Obtain an unknown powdered sample of an OTC pain reliever from your instructor. Record the unknown letter in Data Table 1.
20. Use a spatula to add a few granules of the powdered unknown OTC drug sample to each of the four wells of column 6 of the well plate. Save the remaining amount of sample for later use—in case a test needs to be repeated.
21. Repeat steps 6–9 for row A of the reaction plate. Record observations in Data Table 1.
22. Repeat steps 10–12 for row B of the reaction plate. Record observations in Data Table 1.
23. Repeat step 13–15 for row C of the reaction plate. Record observations in Data Table 1.
24. Repeat steps 16–17 for row D of the reaction plate. Record observations in Data Table 1.
25. Compare your results from the unknown to each of the five known pain reliever samples in columns 1–5. Record observations.
26. Rinse out the reaction plate in the sink, using plenty of tap water. Use a cotton swab to clean the individual wells. Tap the plate dry for use in Part IIa. Empty the test tubes containing the excess powdered pain relievers into a solid waste container. Use these test tubes for Part IIa.

Part IIa. Known OTC Drug Testing—Antacids

1. Place a 24-well reaction plate on a sheet of white paper on the lab bench. Label the sheet of paper as indicated in Data Table 2.
2. Use a mortar and pestle to grind up a single tablet of the first antacid, Alka-Seltzer.
3. Use a spatula to add a few granules of powdered Alka-Seltzer to each of the four wells of column 1 of the well plate. Share the powdered Alka-Seltzer with another lab group as these tablets are large in size. Save the remaining powder in a labeled test tube—in case a test needs to be repeated later.
4. Clean the mortar and pestle by wiping both with a dry paper towel.
5. Repeat steps 2–4 for the remaining two OTC antacid tablets. Place a few granules of powdered Acid Controller Complete in each well of column 2 of the well plate and the powdered generic antacid in column 3. Column 4 will be used for your unknown antacid sample.

• Row A—Appearance/Solubility
  6. Make detailed observations about the appearance of each powder, noting the color and consistency of each. Record observations of appearance in row A of Data Table 2.
  7. Using a dropper pipet, add 10–15 drops of distilled or deionized water to each of the three powders across row A.
  8. Observe any physical or chemical changes that occur as noted by fizzing or dissolving. Record observations in row A of Data Table 2.
  9. Stir each well of row A with a toothpick. Observe and record the solubility of each powdered OTC antacid in Data Table 2. Use the following guidelines to determine the solubility of each.
     • If the resulting solution is clear, then the drug is soluble.
     • If the resulting solution is cloudy, then the drug is slightly soluble.
     • If the powder remains unchanged and there is a thick white precipitate, then the drug is insoluble.
  Note: To avoid contamination while stirring, use three toothpicks (e.g., one for Alka-Seltzer, one for Acid Controller Complete).
• Row B—Acidity/pH
  10. Using a dropper pipet, add 10 drops of distilled or deionized water to each of the three powders across row B. Stir.
  11. Using a different dropper pipet, add 3–4 drops of universal indicator solution to each well of row B. Record the color of each solution in row B of Data Table 2. Be very specific when describing the color so as to distinguish between the wells. Note the approximate pH of each solution by comparing the color to the universal indicator color chart.
  12. Determine an accurate pH of each OTC drug by dipping one end of a strip of 1–12 pH paper into each of the corresponding wells of row B. Save resources by using each end of the pH paper for a different well. Use the color chart on the pH paper tube to determine the pH. Record the pH of each in row B of Data Table 2.
• Row C—Reaction With HCl, “Simulated Stomach Acid”
  13. Using a dropper pipet, add 10 drops of 0.5 M HCl “simulated stomach acid” solution to each well of row C.
  14. Stir each well of row C with a toothpick. Observe any reactions that occur as noted by fizzing (slight or vigorous) or dissolving (insoluble, slightly soluble or fully soluble). Record detailed observations in row C of Data Table 2.
  15. Determine the pH of each OTC antacid in the “stomach” by dipping one end of a strip of 1–12 pH paper into each of the corresponding wells of row C. Save resources by using each end of the pH paper for a different well. Use the color chart on the pH paper tube to determine the pH. Record the “stomach” pH of each in row C of Data Table 2.
• Row D—Reaction With Iron(III) Nitrate
  16. Using a dropper pipet, add 10 drops of 0.2 M Fe(NO₃)₃ solution to each well of row D.
  17. Stir each well of row D with a toothpick. Observe any reactions that occur as noted by fizzing or color changes. Record detailed observations of each solution in row D of Data Table 2. Be very specific when describing the color so as to distinguish between the wells.
  18. Repeat any tests that gave unclear results using the remaining antacids that were saved ealier. Go on to Part IIb—testing an unknown OTC antacid. Do not rinse out the well plate.

Part IIb. Unknown OTC Drug Testing—Antacids

19. Obtain an unknown sample of an OTC antacid from your teacher. Record the unknown letter in Data Table 2.
20. Use a spatula to add a few granules of the powdered unknown OTC drug sample to each of the four wells of column 4 of the well plate. Save the remaining amount of sample for later use—in case a test needs to be repeated.
21. Repeat steps 6–9 for row A of the reaction plate. Record observations in Data Table 2.
22. Repeat steps 10–12 for row B of the reaction plate. Record observations in Data Table 2.
23. Repeat step 13–15 for row C of the reaction plate. Record observations in Data Table 2.
24. Repeat steps 16–17 for row D of the reaction plate. Record observations in Data Table 2.
25. Compare your results from the unknown to each of the three known antacid samples in columns 1–3. Record observations.
26. Rinse out the reaction plate in the sink, using plenty of tap water. Use a cotton swab to clean the individual wells. Tap the plate dry. Empty the test tubes containing the excess powdered antacids into a solid waste container.

Student Worksheet PDF

11856_Student.pdf